Speciation determination of chromium using 1,4-diaminoanthraquinone with spectrophotometric and spectrofluorometric methods.

A highly sensitive and selective method has been proposed for speciation determination of trace amounts of Cr(III) and Cr(VI) in water samples using 1,4-diaminoanthraquinone (1,4-DAAQ). The method is based on mixing an organic phase containing 1,4-DAAQ with an acidic solution (pH 1) of Cr(VI), which is accomplished with absorbance decreasing or luminescence quenching of the organic phase due to a partial oxidation of the 1,4-DAAQ content. After oxidation of Cr(III) to Cr(VI) and determining the total chromium content, Cr(III) content is obtained by subtracting. All of the variables were studied in order to optimize the reaction conditions. No considerable interference was observed due to the presence of coexisting anions and cations. The calibration graphs were linear in the range 3.0 x 10(-7)-3.0 x 10(-6) and 1.0 x 10(-7)-4.0 x 10(-6) M with detection limits of 3.5 x 10(-8) and 2.1 x 10(-9) M for absorptiometry and fluorometry, respectively. Validation of the measurements was confirmed using standard reference materials and a certificated method.